4.
BARREL WALL THICKNESS -- down to 6"
from the muzzle and 6" from the breech

A Good Reason to Own A BoreMaster -- A Personal Experience Worth Sharing
by Bob Foege, BoreMaster Inventor

At
a recent pheasant hunt, one shooter was using a magnificent Parker
12 gauge Frame 4. I routinely use the BoreMaster to measure older guns
– for safety reasons as well as my own curiosity – and I
discovered that this Parker had been drastically cleaned up inside;
bore diameter after the chamber was 0.753" and bore diameter 5"
in from the muzzle was 0.744". Nominal 12 gauge bore size is 0.729".
The barrel wall thickness 5" from the muzzle was 0.023"! Although
the owner was shooting target loads successfully, I warned him against
using heavy pheasant loads and suggested that he have the barrel wall
thickness measured mid-barrel. The photo on the left illustrates what
a 1-1/4 oz. pheasant load did to the left barrel of this compromised
gun. Luckily no person was injured. Although the owner ignored my advice,
the BoreMaster did its job by indicating a potentially dangerous condition.
If the owner had used the BoreMaster when buying the gun he probably
would have wisely declined the purchase.

The
BoreMaster is an easy-to-use and serious tool for the gun owner and gun
trader, providing critical information for all gauges, not generally available
without this tool.

Be sure-don`t guess!

Shoot the right choke for the game or target on hand!

Learn to think of chokes in thousands -- not markings!

With the BoreMaster Shotgun Multi-Bore Gauge, you can answer these questions:
- Have the chokes on a gun been altered from the barrel markings?

- Are the barrels overbored? Original or aftermarket?

- Are the chambers 2" or 2-1/2 "? Have they been altered to 2-3/4" or 3"? Reproofed?
- Is the barrel wall thickness safe (6" from the muzzle or breech)?

We have
measured hundreds of shotgun barrels and have now developed anecdotal
results that we want to share with you.

Remember,
when measuring with the BoreMaster, you CANNOT push into a measurement
– you must insert the probes beyond the measuring point, then
WITHDRAW the BoreMaster, allowing the spring pressure to do the measuring
without interference from your hand.

1. Shotgun
bore diameters are all over the place, varying as much as 2% of nominal
diameter. An example of this is an underbored Perazzi 28 gauge measuring
.537/.538 (nominal is .550), a Browning Double Auto made around 1957
at .720 and a 1964 Browning Superposed 20 gauge at 0.625 (overbored).
The question is how does one confirm that the BoreMaster is reading
accurately? The method we use to verify the bore measurement is by measuring
the CHAMBER dimensions. The chambers are typically held to a very tight
spec which we measure to the thousands. Chamber dimensions are given
in the enclosed literature.

3. RIFLE
BARREL CHAMBERS can be accurately measured. Calibers with case diameters
over .400" – that includes the 30/30 and 30-06 variations
-- and metrics like the 8 mm and 7 mm Mauser and larger can be measured.
Obviously the barrels have to be removed from bolt or lever guns, but
single shots and any break guns are readily measurable. This is an extremely
fast and accurate method of verifying a gun's chamber – especially
unusual metric, Continental, British or obsolete American barrels. It
also verifies if a chamber has been altered to a wildcat configuration.

4. MEASURING
TECHNIQUES. We have found that measuring a handheld or vertical gun
is difficult, resulting in errors. Place the gun (barrels) horizontal
on a table or countertop at rest and insert the BoreMaster probes keeping
them parallel to the barrels. That technique will always result in accurate
and repeatable readings.

5. MEASURING
CHOKES -- The BoreMaster as the "De-Liar." The results obtained
by measuring your fixed or screw-in chokes will surprise you. What one
manufacturer calls Mod is another's I.C. Buy screw-in chokes (12 ga)
designated for steel shot and I.C. may be 0.003" Modified around
0.010" and Full AT 0.018". These are readings from a Perazzi
Mirage with Briley thin wall chokes for steel shot. Those of you with
Polychokes can now accurately find the TRUE choke constriction for each
designation on the Polychoke. These numbers will both surprise and enlighten
you and add to the usefulness of this great product.

6. MEASURING
CHAMBER LENGTHS. When buying or evaluating British and Continental guns,
chamber length is a critical factor in the gun's value. An expensive
side-by-side marked 2-1/2" chamber length on the barrel flats may
be worth its full value until you measure the chamber length with the
BoreMaster and discover that during the gun's life, someone lengthened
the chambers without reproofing the gun. Now what is it worth? Have
the forcing cones been altered?

These aforementioned
measuring jobs are accomplished accurately in a minute, not an hour.
Foremost, the BoreMaster brings accuracy, convenience, portability,
ease of use and the capability to measure all gauges at an affordable
price.

Enjoy your
guns and remember to take a kid out shooting. Our sport needs new blood!

You can
always call us with your questions. Each BoreMaster is tested for operation
and accuracy before it leaves the factory. Your BoreMaster should read
perfectly right out of the box.

Touch
"zero" when the probes are in the bore. Depress probes and
move to the muzzle area of the choke. Read choke constriction (shown
0.021")

Measuring
Barrel Wall Thickness (Optional Kit Required)

You will need the optional BARREL WALL THICKNESS KIT which includes an "O" Ring and the black Barrel
Wall Thickness (BWT) plastic fitting

1.
Fit "O" ring over both probes before pushing on the BWT fitting.
The "O" ring will keep the probes tightly closed.

2. Fit the BWT fitting over the right probe – push on. Make sure
that the BWT offset flat aligns with the bead of the left probe.

3. Push "zero" on BoreMaster control face. Pull back the right
probe several times so that it sets into the BWT device and establishes
a zero point. The zero point may vary by a couple of thousandths. For
the purpose of these measurements, these variances will not matter.

4. Insert the probes over the barrel wall as shown. Allow the BoreMaster
to settle in. Read the results.

Please note: Accuracy is +/- 0.002", however, what you are trying
to establish is the presence of very thin barrel wall thickness, which
this gauge will do.

Please note: If you are reading the choke dimension, remember that you
are reading half of the constriction.

5.
Use the supplied 0.025" calibration strip to confirm the BoreMaster's
BWT accuracy.

6.
After use, remove the "O" ring from the probes to prevent
it from stretching. The "O" ring will need replacing if it
no longer compresses the probes tightly. The "O" ring size
is ½" I.D., 11/16" O.D., and 3/32" thickness.

STANDARD BORE, CHAMBER & CHOKE DIMENSIONS

GAUGE

BORE

CHAMBER

CHOKE

FULL

IMP
MOD

MOD

IMP
CYL

CYL

A

B

C

D

E

F

G

J

K

J

K

J

K

J

K

J

K

10

.775

.841

.933

.8854

2.875

.074

.026

.739

2-1/2

.748

1-7/8

.757

1-1/4

.766

5/8

.775

0

10
MAG

.8379

3.500

12

.729

.798

.886

.8118

2.750

.072

.026

.693

.701

.711

.720

.729

12
MAG

.7968

3.000

16

.662

.732

.820

.7458

2.750

.065

.026

.636

.6425

.649

.6555

.662

20

.615

.685

.766

.6988

2.750

.060

.024

.589

.5955

.602

.6085

.615

28

.550

.614

.688

.6284

2.875

.060

.022

.530

.535

.540

.545

.550

410

.410

.463

.537

.478

3.000

.060

.020

.390

.395

.400

.405

.410

This drawing and the specification information was
released by Ithaca prior to advent of plastic shot protector.

Slightly Imperfect Products:On occasion we have BoreMasters that are
perfectly functional but may have cosmetic flaws. This includes manufacturing
marks, scratches or smudged numbers. When available, they are subject to
a 30% discount off the published price. Please call 800-979-9156 for availability.